Last year I had a friend who went to Cancun with an acquaintance he knew through some friends. Upon re-entering the country in Dallas they both had an X on their customs slip. They were in a group of four. Three of them purchased their tickets together and all three had an X. The fourth person who purchased separately did not. After they cleared customs the acquaintance said that this happened to him the last time he traveled outside the country. He said that he matched a name of someone who was incarcerated (this could potentially be a lie).

Fast forward a few months. My friend was flying back solo from a trip to Iceland and had an X on his customs slip. Then a few months later coming back solo from Peru the same thing happened. He applied for global entry and was denied before being interviewed. Today he contacted me because he is leaving for Madrid and they called his name at the airport and had to double check his passport.

Any idea what is going on? Can he get any further information?